1. Field of the Invention
The present invention relates to a bumper reinforcing structural unit placed behind the bumper facia to absorb impact loads.
2. Description of the Related Art
FIG. 6 shows a cross sectional view of an impact absorbing arrangement for a passenger vehicle, disposed at the front and rear of the vehicle, including a bumper facia 102 arranged beneath the body panel 100, and a reinforcing member 104 placed behind the rear surface of the bumper facia 102 to protect the body panel 100 from potential damage. The reinforcing member 104 is attached to a transverse member 108 via a bracket 106. In recent years, traditional metal structure has been replaced with structural polymers to reduce the weight and improve the corrosion resistance of the reinforcing member 104.
In a Japanese Laid-open Patent Publication (JLPP), H3-227750, a molded resin reinforcing structure is disclosed, which is comprised by an upper plate, a lower plate and a vertical wall to close the back while leaving the front open, and the internal space is divided by partition plates.
Another JLPP H6-298018 discloses a bonded reinforcing structure comprised by a channel shaped member bonded to a separate reinforcing-plate to reinforce the back side of the channel shaped member. Depression sections are provided in lateral positions of the reinforcing unit having a hole for attaching the structure to the chassis. Also, a JLPP H9-226484 discloses a reinforcing structure in which the open section is totally closed with a separate plate member.
These structures share a common feature that the center front section is shaped as a protruding arch, and the reinforcing member is attached at its transverse ends to the chassis. The aim is to absorb the impact energy applied to the bumper first by elastic deformation followed by further plastic deformation of the reinforcing member, if necessary.
Such conventional designs present some advantages as well as disadvantages. Those types, typified by JLPP H3-227750, having a closed back and an open front, have a problem of weak resistance to frontal impact load, and, to compensate for the frontal weakness, the overall structure is strengthened by increasing the component weight so as to be able to absorb a given amount of impact energy. Those with a complete open back, typified by JLPP H6-298018, tend to open outwards when a frontal load is applied. To compensate for this weakness, a reinforcing-plate is attached to the open back, but because it is a separate member, it offers limited impact absorption and presents a problem of increasing the number of assembling steps required. For the design disclosed in JLPP H9-226484, although the strength is adequate because the back surface is completely closed by a reinforcing-plate, assembling steps as well as its overall weight are increased.